If you do not have the MS Office installed on your computer then do not worry. Here are some online tools that you can use to open excel files online.
Note: Please do not open sensitive and confidential files on any of these online tools.
This is the official Microsoft Office website that you can use it to open excel files online.
You can choose a file or import from a URL. Zoho supports Xls, xlsx, ods, CSV, and tsv formats.
Offidocs.com helps you create XLS spreadsheets that are similar to MS Office.
Aspose has an XLS viewer and also an editor.
You can view and edit excel sheets using a browser like Chrome or Firefox on Groupdocs.app.
And of course, there is Google Spreadsheet that you can use it to open, create, and even edit excel sheets online. It supports .xls (if newer than Microsoft Office 95), .xlsx, .xlsm, .xlt, .xltx, .xltm .ods, .csv, .tsv, .txt, .tab
I will update you with more websites similar to these, very soon. Please do share it with others if you found it useful.